Here's what I really want to know: If I'm doing fairly typical editing work in VisualEditor, and I insert a template, how likely is it that I'm going to get (some, ideally complete, correct, and useful) TemplateData? And if the answer is anything other than "Very high likelihood of good TemplateData existing", then what are the templates that should most urgently be fixed?
I imagine that the result from this task will be a list of the top 1000 directly transcluded templates, or the top 10%, or templates that are used more than some sensible amount of times, or something like that. I think that the main problem will be getting the templates that editors insert into the mainspace, and not the meta-templates like {{ambox}} and {{navbox}}.
I would like the list to indicate which ones have TemplateData (either on the template page or on a transcluded subpage, like /doc). I assume that it's not possible to figure out which ones have complete TemplateData.
I need this for en.wp (the sooner, the better). I would also like to have this for another dozen large communities (de, es, fr, ja, ru, it, zh, pt, tr, nl, pl, ar). At most of these communities, if I can get the list, I can get people to add the TemplateData.